The present invention relates to an automobile interior board and more particularly to an automobile interior board obtained by complexing bamboo fiber, natural material-derived fiber and biodegradable fiber with each other.
In recent years, biodegradable products have been noted from the standpoint of protection of global environment, particularly waste disposal. Biodegradable products are advantageous both in convenience of themselves and environmental adaptability for degradation of waste to water, carbon dioxide, etc. by the action of microorganism such as bacteria. The development of various merchandises as automobile interior board such as ceiling substrate have been extensively attempted.
An automobile interior board needs to be sufficiently treated in protection of global environment, particularly waste disposal, be easily produced, cause passengers to have no feeling of physical disorder and show no sagging particularly when used as a ceiling substrate. As such automobile interior boards there can be used the following various fiber-complexed resin products <1> to <5>.    <1>: One obtained by dispersing a thermosetting resin such as phenol resin in a natural fiber such as hemp and cotton as a binder, heat-pressing the dispersion in a mold to form a required roughened shape, setting the shape in a bonding mold with a surface material such as nonwoven cloth and fabric, and then bonding the surface material to the shape with an adhesive.    <2>: One obtained by in-mold foaming a glass fiber-filled foamable PP resin with a surface material such as nonwoven cloth and fabric to form an integrally molded material.    <3>: A molded ceiling substrate having a foamed sandwiched structure having a film layer provided on the both surfaces of a foamable sheet-shaped material such as styrene with an adhesive.    <4>: One including as a core a slab urethane, a glass mat bonded to the both surfaces of the slab urethane with an adhesive, and a surface material such as nonwoven cloth and fabric bonded to the outer side of the glass mat with an adhesive.    <5>: One including as a core an engineering plastic foamable material having a high rigidity such as modified PPO and modified PPE and a surface material such as nonwoven cloth and fabric bonded to the outer side of the engineering plastic foamable material with an adhesive.
An example of related fiber-complexed resin products and producing methods thereof are disclosed in JP-A-2004-284246. JP-A-2004-284246 discloses a fiber-complexed resin product including a base layer having a desired strength attained by a relatively rigid fiber and a surface layer having a smooth surface attained by a relatively flexible fiber. In particular, both first and second fibers are a natural material-derived fiber based on vegetable or animal material and both first and second thermosetting resins are a natural material-derived resin. Both the fiber and resin are biodegradable and thus can be subjected to biodegradation before discarded.
However, when the aforementioned related fiber-complexed resin products are used as automobile interior board, the following problems arise.
The method of producing the fiber-complexed resin product including as a binder a thermosetting resin such as phenol resin as in Clause <1> requires the use of two molds, i.e., mold for molding a substrate having a required roughened shape and bonding mold for bonding a surface material such as nonwoven cloth and fabric to the substrate and hence two steps. It is also required that the molding temperature be not lower than 200° C., at which the thermosetting resin is heat-cured, increasing the temperature and time required for molding and hence the working cost and labor cost. Further, the resulting fiber-complexed resin product contains a large amount of a phenol resin and hence free formaldehyde or phenol that evaporates to give an environmentally unfriendly atmosphere. Moreover, this product can be difficultly recycled at disposal because it is composed of a thermosetting resin.
The molded ceiling substrate as described in Clause <2> must be thick and heavy to obtain a required rigidity. The molded ceiling substrate is also disadvantageous in that the dimensional shrinkage after heat molding is great. Further, since the molded ceiling substrate contains glass fiber, it is attached to the wall of the incinerator when combusted for disposal, giving damage to the incinerator. Moreover, even when the molded ceiling substrate is crushed and melted in an attempt to recycle the molded ceiling substrate, the glass fiber is cut, making it impossible to recycle the molded ceiling substrate.
The molded ceiling substrate as described in Clause <3> is a sheet made of a thermosetting resin foamable material that can be difficultly heated uniformly to the core thereof. Further, the molded ceiling substrate must be heated under severe conditions because the sheet shows drawdown as the temperature rises with heating. This requires an expensive heating device such as high precision temperature controller such as infrastein heater, adding to initial cost. The molded ceiling substrate is also disadvantageous in that the dimensional shrinkage after molding is great. Further, since the molded ceiling substrate contains an organic solvent as a foaming agent, the product contains a slight amount of the organic solvent even after molding, increasing VOC (volatile material) in the automobile cabin and giving an environmentally unfriendly atmosphere.
The fiber-complexed resin product as described in Clause <4> includes urethane as a thermosetting resin and even a glass mat and thus can be practically not recycled. When the fiber-complexed resin product is discarded and combusted, the glass is attached to the wall of the incinerator, giving damage to the incinerator. Further, harmful VOC such as catalyst amine is produced, giving an environmentally unfriendly atmosphere.
The fiber-complexed resin product as described in Clause <5> includes an expensive engineering plastic foamable material that adds to the part cost.
In the foregoing description, the formation of the fiber-complexed resin products as described in Clauses <1>, <3>, <4> and <5> requires the use of a bonding step involving the use of an adhesive and hence a complicated step. Further, all the resin-complexed resin products of <1> to <5> include petroleum-derived materials that cannot be degradated even when discarded for reclamation and cause an environmental problem involving the rise of carbon dioxide on the earth even when combusted.